Field of the Invention
The present invention relates to a polishing plate adaptable to polishing the surface of synthetic resins and to methods for polishing synthetic resin surfaces. More in particular, the invention relates to a polishing plate in which a polishing agent is conducted outwardly from the center of a polishing plate and to methods of polishing employing such a device.
The demands made on the quality of synthetic resin surfaces, particularly when sheets of synthetic resin are to be used for glazing, for instance in the construction of aircraft, are extraordinarily high.
The classic method for finishing synthetic resin surfaces is by grinding and polishing. Because of the temperature sensitivity of the synthetic resin, grinding is as a rule carried out with ample water cooling. The grinding pressure is kept low in order to avoid a clogging or seizing of the grinding wheel. Polishing is preferably carried out using a circular movement and a disc of felt, plain cortan fabric in a tabby weave, or molleton, which revolves at a speed of about 25 to 30 meters per second.
In principle, grinding and polishing apparatus known from metal working can be employed. Polishing machines in which an aqueous solution of a polishing agent is led from the center of a rotating polishing plate are part of the state of this art.
The agents and apparatus of the prior art can not fully satisfy the exacting requirements invalued in polishing synthetic resin surfaces, particularly the demands made on transparent synthetic resins for glazing, especially in aircraft construction. The surfaces which are polished by machine after prior grinding are, on the average, by no means perfect. Thus, it has often been necessary to remove surface defects, for example numerous grinding scratches, by hand polishing. Thus, there was presented the problem of developing a grinding apparatus which, by the lowest possible expenditure for apparatus and construction, would successfully accomplish the polishing of synthetic resin surfaces of the quality desired.